Premature infants possess in varying degrees, undeveloped lungs. Very low birth weight infants ("neonates") with undeveloped lungs cannot obtain enough blood oxygen on their own and often suffer from complications such as bronchopulmonary dysplasia (BPD), pulmonary edema and respiratory distress syndrome. These are phenomena occurring when the immature lung does not have the ability to maintain the lung air sacs in an open position due to the lack of surfactant, which coats the inner lung that captures oxygen. Sometimes the lungs become flooded with fluid. In addition, the lung cells do not have adequate defense mechanisms in place to deal with the toxic effect of oxygen in the inspired air.
Bronchopulmonary dysplasia is the abnormal growth or development of the bronchial tubes and the lungs. Presently, there is no suitable treatment for chronic BPD.
Respiratory distress syndrome is caused by a deficient secretion of surfactant from alveolar cells. This lining may not be present in the lung of a premature infant. Without adequate surfactant, the infant will have difficulty breathing normally. Adults can be cured with surfactant therapy, which is the administration of animal surfactant (typically porcine) to the airways. However, surfactant therapy is less effective in neonates, particularly those with respiratory failure caused by factors other than, or in addition to, surfactant deficiency.
Pulmonary edema is caused by a seepage of fluid into the air sacs of the lungs and into the tissue forming the framework of the lungs. The lungs become swollen, resulting in a shortness of breath and congestion.
Presently, the preferred form of treatment for the above-mentioned complications is to intubate the premature infant, i.e., to apply mechanical ventilation apparatus that forces oxygen through tubes leading through its throat to its lungs. With such ventilation, the low birth weight premature infant can obtain limited oxygen. This invasive mechanical procedure is frequently the only treatment for infants with undeveloped lungs.
However, when an infant's lungs are forcibly ventilated under the present form of treatment, the infant is introduced to medical complications that jeopardize its life or long-term health. Also, in some cases where premature neonates are mechanically ventilated, they become dependent on the mechanical ventilation for survival.
Many of these premature neonates with undeveloped lungs contract and suffer from chronic disease or in some cases, suffer death, due to the limitations of prior art treatment methods and apparatuses for augmenting blood oxygenation. On the other hand, without assistance of mechanical ventilation, the undeveloped lung is unable to properly oxygenate the infant's blood, as noted above. This is likely to cause, if not death, serious neurological deficits in the infant's growth and development--an unacceptable alternative.
There has long been a need felt in the medical community to eliminate the risks and problems of mechanical ventilation of premature or low birth weight infants associated with the present treatment art. All the following conditions, diseases or syndromes are known risks associated with the present art that need to be minimized or eliminated. These disorders or conditions are caused by lung exposure to high doses of oxygen and other side effects of the current treatments, and can lead to serious mortality and complication rates in prematurely born infants.
Bronchiolitis, the acute inflammation of the bronchioles is one known side effect of existing methods of neonatal oxygen therapy. If the bronchioles are inflamed, the passage of air is blocked between the windpipe and the lungs and breathing is thereby complicated.
Both lung and other organ damage are caused by hyperoxia. Hyperoxia is a condition in which the blood carries more than the usual amount of oxygen. It is caused by the inhalation of pure oxygen. The risks and problems of the prior art associated with infant hyperoxia are commonly known to those in the medical profession.
Central nervous system damage and pulmonary oxygen toxicity are caused by prolonged exposure to oxygen when a patient is mechanically ventilated. Pulmonary oxygen toxicity is a condition where the lungs are poisoned because they are saturated with above normal concentrations of oxygen.
Retinopathy is caused by exposure to high concentrations of oxygen. It is a disease of the retina or the innermost, image-receiving wall of the eyeball.
Intraventricular brain hemorrhaging and seizures are other common complications that effect premature neonates that are mechanically ventilated.
It is not disputed that present treatment methods help a large percentage of neonates with undeveloped lungs. However, many other premature infants are not cured or helped and still others have their health impaired by the side effects of such treatment. Medical literature suggests that there is a great need tier an effective alternative to the unnecessary infant disease and death caused or exacerbated by these invasive mechanical ventilation procedures, which contribute to pulmonary oxygen toxicity. Despite progress in this field, low birth weight infants continue to suffer serious neurological deficits in growth and development.
Heretofore unrelated to the treatment of premature infants is the field known as hyperbaric medicine or hyperbaric oxygen therapy. This is the use of intermittent, high dose (100%) pressurized oxygen breathing to treat certain diseases which are characterized by a relative tissue hypoxia (under-oxygenation). For example, hyperbaric medicine is used in the treatment of problem wounds. In the present hyperbaric art, the oxygen breathing must be intermittent, since high doses of oxygen are toxic to both the lung and the brain, as noted above, even in adults.
In conventional hyperbaric medicine, oxygen is delivered to the blood through the lungs, as opposed to through the skin. Problem wound healing is promoted by dissolving oxygen in the blood under pressure (which pressure allows it to contain higher oxygen concentrations than normal). This is done to the point where the partial pressure of oxygen in the blood becomes very greatly elevated. The induced partial pressure differential causes increased amounts of oxygen to escape into the wound tissue at adjacent capillaries. Thus, oxygen is delivered to the wound internally, rather than transcutaneously. The oxygen is administered at a high dose by enclosing the entire patient in an airtight chamber and increasing the pressure to two to three times the normal atmospheric pressure. The duration of treatment typically is once or twice daily for one to two hours.
Heretofore, hyperbaric concepts have not been applied to the field of neonatal medicine. Indeed, conventional thinking would suggest that such would be particularly inappropriate, insofar as the breathing of high dosage oxygen is largely what causes the problems discussed above. However, with modifications discussed herein, it is submitted that hyperbaric principles can be adapted to the avoidance of oxygen and other ventilation damage to neonatal lungs.
Prior developments in this field may be generally illustrated by reference to the following information disclosure statement:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 5,207,639 W. Cooper May 4, 1993 5,308,310 T. Roff et al. May 3, 1994 5,218,958 W. Cooper Jun. 15, 1993 4,296,743 R. Lasley Oct. 27, 1981 3,889,670. S. Loveland et al. Jun. 17, 1975 5,336,616 S. Livesey et al. Aug. 9, 1994 Re. 34,077 P. Segall et al. Sep. 22, 1992 5,084,011 D. Grady Jan. 28, 1992 3,158,150 F. Croasdaile Nov. 24, 1962 ______________________________________
U.S. Pat. No. 5,207,639 teaches a device for oxygenating the blood of a non-breathing prematurely born baby via its umbilical cord.
U.S. Pat. No. 5,308,310 teaches a plethysmograph system for monitoring the respiration of neonates. It features an air-tight transparent acrylic case which is able to withstand at least some internal air pressure increase of unstated quantity. The pressure changes discussed therein appear solely caused by the natural and/or mechanically-induced respiration of the infant.
U.S. Pat. No. 5,218,958 teaches a life support system for a premature baby that supplies oxygen and nutrients to the child. An air-tight upper chamber contains 100% oxygen which is supplied to the infant via its still-connected placenta.
U.S. Pat. Nos. 4,296,743 and 3,889,670 teach hyperbaric devices. The former may be modified to provide oxygen treatment to any portion of the patient's body except the head. The latter is a hyperbaric ventilator that fits on the head only. Both operate at pressures of 50 pounds per square inch, which is about 3 atmospheres absolute (ATA).
U.S. Pat. No. 5,336,616, U.S. Pat. No. Re. 34,077 and U.S. Pat. No. 5,084,011 teach oxygenating blood and tissue and, along with U.S. Pat. No. 3,158,150, are representative of what is in the art.